Acid regeneration system

An acid regeneration system has been installed to regenerate spent pickle liquor for reuse on-site. 

EARS [Enhanced acid regeneration system] A process for recovering hydrochloric acid from the ERMS ilmenite beneficiation process. It may be used also for recovering waste pickle liquor. The acid liquor containing ferrous chloride is evaporated at low temperature to form iron chloride pellets, which are fed to a pyrohydrolysis reactor. This generates hydrochloric acid and iron oxide pellets, which can be used for steel production or disposed of as inert landfill. Developed by E. A. Walpole at the University of Newcastle, Australia, from the early 1990s and piloted by Austpac Gold (now Austpac Resources). 

In a process variant (Enhanced Acid Regeneration System EARS process), the ilmenite is roasted to convert the titanium component into the insoluble rutile form and to condition the iron component for leaching. The product is then rapidly leached at atmospheric pressure in hydrochloric acid to remove the iron, leaving rutile crystals in the former ilmenite grain. This synthetic rutile (typically 96-98% Ti02) is then washed, filtered, and calcined. The iron chloride leach liquors are processed to regenerate the acid, and the iron oxide pellets can be sold for use by the steel or cement industries. 

De-alkalization resins must not be over-regenerated or the product water becomes strongly acidic. The system therefore needs some measure of skilled supervision, and may depend on a pH meter - an instrument that, in turn, needs regular and skilled maintenance. 

Another recent new application of a microporous materials in oil refining is the use of zeolite beta as a solid acid system for paraffin alkylation [3]. This zeolite based catalyst, which is operated in a slurry phase reactor, also contains small amounts of Pt or Pd to facilitate catalyst regeneration. Although promising, this novel solid acid catalyst system, has not as yet been applied commercially. 

D. Mandler and 1. Willner, Photosensitized NAD(P)H regeneration systems application in the reduction of butan-2-one, pyruvic, and acetoacetic acids and in the reductive amination of pyruvic and oxoglutaric acids to amino acids,... 

For the regeneration of ATP, we chose the system based in the use of acetyl phosphate as final phosphoryl donor because this affords several advantages (i) acetyl phosphate is easily obtained by acylation of phosphoric acid with acetic anhydride in ethyl acetate [24], and (ii) the resulting sodium acetate is a non-toxic and an environmentally compatible compound. However, this regeneration system is quite sensitive to pH changes. Thus, a continuous adjustment of the pH to 7.5 is needed to maintain the proper operation of the system. Perhaps the main aspect of this approach is that the DHAP must be formed at the same rate as it is consumed by the aldolase. To avoid the accumulation of DHAP and minimize its non-enzymatic degradation, fine tuning of the aldolase/DHAK activities is needed. This adjustment must be experimentally optimized for some acceptors. 

Both of these processes direct the SO2 absorbed from the FCCU flue gas to the refinery SRU, where it is converted to elemental sulfur and added to the marketable sulfur that is generated by the SRU from H2S. Alternately, the SO2 can be converted to sulfuric acid in a dedicated sulfuric acid plant, or in combination with an existing refinery spent acid regeneration unit. When the SO2 is directed to the SRU, 1 ton of SO2 captured in the scrubber is converted to 0.5 tons of marketable elemental sulfur and less than 0.1 ton of sodium sulfate waste is generated per ton of SO2 absorbed. In an acid plant, 1 ton of SO2 generates 1.5 tons of 98% sulfuric acid. Steam is also generated from the conversion of SO2 in both the SRU and the acid plant, which moderates somewhat the steam consumption rate of the solvent regenerator for both the LABSORB and CANSOLV systems. 

This AQUATECH acid recycle system is the first of its kind in the world. It was designed to recycle 1.6 million gallons of waste acid a year, recovering 90% of the total fluoride and nitrates resources. The waste volume is reduced by 90% to the resultant solid metal hydroxide cake which is then recycled to the furnace. Over the past two years of operation, the system successfully reduced the acid waste hauled. Actual waste acid processed versus acid product regenerated are tracked in Figure 8. 

Recommended reference operating conditions for Cu precipitation in the pilot plant system include a 90Z to 100Z stoichiometry, initial Cu concentrations of 150 to 180 g/L, and crystallization periods of 24 hours. A seed solution will not be necessary. Also, reaction temperature has no effect on Cu removal or efficiency of acid regeneration for solutions containing 100 or 150 g/L Cu. 

The enzymatic preparation of the activated sugar nucleotide may also involve a cofactor regeneration system. An example of this is an economic one-pot procedure, in which N-acetylneuraminic acid (NeuAc) is generated in situ from IV-acetylmannosamine (ManNac) and pyruvate with sialic acid aldolase and then converted irreversibly to CMP-NeuAc ([14], see also Sec. III). 

Figure 3 shows the results obtained for the benzene-water system and compares these with the results from the benzene-water-hydrochloric acid system. The acid-free system exhibited the almost linear adsorption isotherm expected at low water concentrations, while the data from the acid system, although somewhat scattered, suggest that the adsorption capacity was increased when some HC1 was present. In any case, the feasibility of using Z200H to dehydrate the benzene-hydrochloric acid system was demonstrated, and justified embarking on regeneration and dynamic equilibrium test studies. 

Fig. 39. C02-fixation by coupling carboxylato biocatalysts to the photochemical NADPH regeneration system. C02-fixation products are subsequently coupled to the biocatalyzed photosynthesis of aspartic acid...

---